Back to the main site

Yamaha F70 rpm range issues

TexAgg56

TexAgg56

Well-Known Member
Messages
152
Reaction score
158
Location
Texas
I have a new Yamaha 70 on a 20SLX and it won't go above 4200 rpm. Only at 10 hours on breaking it in. Is this normal? IS there some sort of limiter kicking in early? Everything I am reading says it should be 5300-6300 at WOT?


Could a better performance prop help that much? It has a SS prop on it now. Not sure of the specs. Trying to find that out now.


Thanks for any advise for this newb!
 
Sounds like something is out of whack! Ask your dealer what prop is on the boat and verify it, the mounting height discussions you may find would not have that much of an impact. I'd say with a prop issue or a motor issue. I'd be knocking on the dealers door to get it straighten out right away as they should have water tested it. 
 
Sounds to me like you might have the wrong sized prop. A lower pitch will increase your RPMs. 
 
been reading other threads on other various boards.  I may be "over propped". This was a "display window boat". Already had a nice new shiny SS "big" prop when I got it! Silly me! I figure when they....whomever "they" are....basically set the boat up in the beginning they just grabbed something that fit the F70 and ran with it. It looked "perdy"! It was never intended for actual water use anyway. It was the "display boat".  So now I am on a "prop quest". 
 
A SS on a 90? Hmm, don't see that very often...
 
Michiman said:
A SS on a 90? Hmm, don't see that very often...
Click to expand...

Even less on a 70! 


If you look on the prop a lot of them have the specs stamped into it. IMHO it is completely pointless to have a SS prop on that. 


What speed were you going?  It is also possible that the RPM gauge is incorrect. I know a few on here had that issue (I think there was two switch settings or something) 
 
well that was kind of my point. Pretty useless at a whopping 17-18mph @ 4200.  Just for performance on the engine and running at optimum efficiency.  Not really interested in top speeds! Max effectiveness on max rpm's. I'd think I could at least get too 21-22mph @ 6000+. So I think it's just been over propped for looks. Just going to get a stock factory and go from there. maybe a 14/13.
 
Boat goes in on the 20th for the 20-hour maintenance. Dealer will be dealing with all that then.  I've taken it out 3 times since. Even with just myself, my wife, our dog and 1 cooler, I'm barely hitting 4300rpm. GPS speed about 18. So I'm 99% sure it's a prop issue. I'm thinking I should be around 5800-6000rpm and maybe 21-23mph at WOT.
 
Not the exact match, but close enough.  Check what prop you have on it.  Here's a Yamaha Performance Bulletin on a T60TLR pushing a 22 SLi with a 14" / 11 pitch prop aluminum prop.  Your specs are for 5300-6300 RPM for that motor (assuming it's the brand new version):


http://yamahaoutboards.com/sites/default/files/bulletins/bulletin_4stroke_highthrust_dt_sab79a.tmp.pdf


Here's the spec sheet from Yamaha


http://yamahaoutboards.com/outboards/Midrange/specifications#node-4743


Impressive little motor!  Only weighs 257 lbs - that's over 100 lbs lighter than the 75 HP and only 6 lbs more that the 60 HP.  Nice little sweet spot!


Match this up with the Talon Pontoon SS Prop (I'd go with the 11 pitch) and you'll have a great combination:


Talon Pontoon (SDS) (Stainless Steel)
Designed to meet the specific needs of midrange-powered pontoon boats, the Talon Pontoon Propeller provides maximum performance and efficiency. Equipped with Yamaha’s exclusive Shift Dampener System, they fit Yamaha T50, T60 and F70 - F115 four-stroke engines, as well as 60 hp – 130 hp two-stroke Yamaha outboards. Talon Pontoon propellers are available in 9”, 10”, 11”, 12” and 13” pitches.
 
Last edited by a moderator:
Dealer will have to research the prop. I have looked all over this one. Not a single number or digit or stamping of any kind.....anywhere. It's a mystery prop! So once the dealer pulls it we may know. Other than that.  Once I rule out faulty gauge. And they hook the engine up to the computer. My money is on a new performance pontoon prop. Even if we can't find out what this one is. I'm not leaving it on my engine! Getting a new prop regardless. At least I'd know what I have.
 
You must log in or register to reply here.
Back
Top